Method of dispersing flocks of agglomerated fibers in pulp conveyed to a paper machine



Apnl 27, 1965 K. A. SKARDAL METHOD OF DISPERSING FLOCKS OF AGGLOMERATEDFIBERS IN PULP CONVEYED TO A PAPER MACHINE Filed Jan 25 1963 INVENTOR. KL. ARV/D SKARDAL BY W 71- Q A TZ'ORNEY,

United States Patent 3,180,788 METHOD OF DISPERSING FLOCKS F AGGLGM-ERATED FIBERS IN PULP CONVEYED TO A PAPER MACHINE Karl Arvid Skardal,Stockholm, Sweden, assignor to Aktieholaget Celleco, Stockholm, Sweden,a corporation of Sweden Filed Jan. 23, 1963, Ser. No. 253,372 Claimspriority, application Sweden, Jan. 26, 1962, 847/62 4 Claims. (Cl.162-216) In order to achieve in paper making the greatest possibleuniformity in respect of the distribution of fibers in forming the paperweb, it is inter alia of importance that the pulp supplied to theendless wire does not contain flocks of agglomerated fibers ofsubstantial size. Insofar as the pulp conveyed to the paper machinecontains such flocks, it 1s thus highly desirable that said flocks willbe dispersed in some manner before the pulp reaches the wire. It is alsosuitable to carry out this dispersion so close to the wire as to preventnew formation of flocks. Many arrangements for this purpose have beensuggested, mostly however without satisfactory results.

An arrangement of this kind which has been used for several decades andstill is used, consists of a hollow cylinder having a perforated shell,which is mounted in the inlet box across the direction of the main flowso as to take up part of the cross-section only, and which is rotatedaround its central axis. The purpose of this cylinder is to cause thepulp to enter the drum through the holes or apertures in the part of theshell, which during the rotation momentarily faces the direction offlow, and to be discharged through the holes at the opposite side of theshell, so that the flocks will be dispersed due to the turbulent flowthus achieved.

In practice, however, it has been proved that only a ratherinsignificant portion of the pulp passes through the hollow cylinder,which only partially spans the path of flow of pulp to the papermachine, whilst the main portion will pass outside said hollow cylinder.This seems to be due to the possibility for such by-passing onone handand due to the resistance against radial passage from outside and insidethrough the holes of the cylinder, on the other hand, due to the effectof the centrifugal force on the pulp penetrating into the holes. Oftenno difference can be observed in paper produced with or without suchhollow cylinder in the inlet box.

The main object of the present invention is to provide an appreciablymore rational method-as compared with earlier known methodsto achievedispersion of flocks in the connection now referred to. To this purposethe pulp, during its passage through the inlet box of the paper machinepreferably in the vicinity of the outlet of the inlet box to the endlesswire, is passed through a system of two perforated walls placed close toeach other whilst relative movement is maintained between said walls indirection parallel to the planes of the walls.

The invention will now be described more in detail with reference to theenclosed dravw'ng, in which:

FIG. 1 illustrates a cross-section of part of the arrangement forcarrying out the invention;

FIG. 2 illustrates a side-section of an inlet box having a completearrangement for carrying out the invention;

FIG. 3 illustrates a plan view of part of the inlet box according toFIG. 2 and FIG. 4 illustrates a side-section of a modified embodiment ofthe arrangement according to FIG. 1.

All figures are diagrammatic and only serve as examples, withoutrestricting the invention. Identical parts are indicated with the samereference numerals in the different figures.

In FIG. 1 two perforated walls 1 and 2 are situated close 3,180,788Patented Apr. 27, 1%65 to each other, one wall 1 being displaceablealong the other wall 2 in the direction of the arrow 3 at a speed Crelative to the latter wall. In this direction of movement the holes orapertures of the walls have a width which in the wall 1 between thebordering edges 4a and 4b has the size D and in the wall 2 between thebordering edges 5:: and 5b have a substantially smaller size d. Pulp ispassed through the Walls in the direction of the arrow 6 at a speed Cand between the walls there is a very small interspace not shown in thefigure suflicient to give space for the thickness of individual fibers.The arrangement operates in the following manner:

Each time when during the movement of the wall 1 an edge 4a passes anedge 5b, flocks of fibers, which together with the pulp on the way inthrough the walls, to some part come between said edges, will be tornapart by the cutting effect of the edges, whilst individual equallypositioned fibers will only be subjected to a temporary bending effect.If in every passage-hole S the edge 5b is passed by an edge 4a atshorter time-interval than the time a flock of unpermissible sizerequires to pass entirely from the mouth of the passage-hole into thehole, there will be achieved full security against no such flockescaping said tearing effect. If the extension of the flock in thedirection of flow 6 is designated L, this condition will be fulfilled inthe equation (D+d) /C L/C as it will be realized from FIG. 1.

It is thus obvious that it is of importance to keep the size of theholes small in orderat certain relative speed C and passage speed C todisperse even very small flocks. The possibility for this, however, islimited, because the holes in the wall 1 must be sufficiently wide so asnot to be clogged by larger flock-formations, but in any circumstancespermit passage of such flock-formations for shredding or rubbing againstthe wall 2 so as to initiate the dissolution of the flocks by shreddingagainst said wall and to maintain the passage of the pulp. The wall 2,however, can be provided with small holes, which are suitable from thepoint of view of manufacture and can thus also be constructed as asieve-wall as a precaution against possible occurrence of alien solidmatter in the pulp. With predetermined Widths of the holes differentdemands can be met in respect of flock dispersing effect by selectingdifferent ratios between the relative and the passage speed. As examplesof practical hole-Widths can be mentioned that D may be approximately 20mm. and d approximately 3.5 mm. It is to be pointed out, however, thatin principle nothing prevents achieving dissolution of the flocks evenwhen the holes in the Wall 2 are large. The required magnitude of theratio C/C will be much greater, however, which at unchanged relativespeed and requirement for dispersing effect means equally reducedcapacity. The passage-holes can naturally be shaped in manifold ways,for example circular or square, or may be extended longitudinallytransversely to the relative movement.

In the complete arrangement according to FIG. 2 a partition-wall 8divides the inlet box 7 into an inlet chamber 9 communicating with theinlet ll) of the inlet box for pulp and an outlet chamber 11communicating with the outlet 12 of the inlet box to the endless wiregauze 13. In the partition wall 8 there is a passage-hole 14, and abovethis a cap or hood system of two concentric drums arranged close to eachother, namely an outer drum 2a having passage-holes 5 and an inner drum1a having passage-holes 4, which correspond to the walls 2 and 1,respectively, in FIG. 1. The outer drum is rigidly connected with theinlet box by means of a frame 18 with attachment means in the form of aflange 15. The inner drum is rotatably mounted in the frame and providedwith driving shaft 16, coupled to some driving power source of knownkind, not shown in the figure. By this device, pulp passing through theinlet box from the inlet It) to the outlet 12, is forced to flow throughthe walls of the drumsystem, as indicated by the arrows, the flocksbeing dispersed as described with reference to FIG. 1, whereby therelative speed easily can be varied on changing the speed of rotation.By dispersing the flocks close to the outlet to the endless Wire, thepossibility for subsequent new formation of flocks will be utterlysmall.

In addition to the advantages concerning the dissolution step, thearrangement now described also otters the special advantage that byrotation of the Wall 1a and thus also by rotation of the pulp caught inthe holes 4, the pulp will be forced through the walls under theinfluence of the centrifugal effect. On one hand this results in agreater security against clogging of the holes 4 and on the other handthe throttling losses in the system can be counterbalanced to a greateror lesser degree and possibly overcome by pumping-effect in the system.

Through a hole 17 in the inlet box, which is wider than the outerdiameter of the outer drum-and upon loosening the flangethe entire drumunit can be removed from the inlet box and reinserted into the same.Thus, the entire drum-system forms a separate unit, which can be easilybuilt-in into the inlet box and removed again, for example foradjustment or repair purposes. In most cases and particularly in thecase of a wide wire gauze and long inlet box it is suitable to build ina plurality of such units side by side as shown in FIG. 3. In thismanner, merely by varying the number of units, the system can be adaptedto different widths of wire gauze, which entails appreciable advantages.

FIG. 4 illustrates that in principle it is also possible to mount theouter drum 2a rotatably in the frame 180, driven by the axis 16a, whilstthe inner drum 1a is rigidly connected with the partition wall 8 sincethe relative movea ment can also be obtained in this manner. However, inthis case it is not possible to obtain the special advantages in respectof security against clogging and the possibility of easy dismounting,which are characteristic for the previous arrangement.

Naturally, it is also possible to arrange the drum-system with itscentral axis directed towards another direction than the vertical one,for example horizontally, in connection with causing passage of the pulpthrough a vertical part of the partition wall in the inlet box.

What I claim is:

1. A method for dispersing flocks of agglomerated fibers in pulpconveyed to a paper machine so as to pass through a head box providedwith an outlet discharging the pulp from the head box to the wire ofsaid paper machine, comprising the steps of causing the pulp in saidhead box to flow towards said outlet through two perforated walls insuccession while crossing a small interspace between said walls, saidinterspace being dimensioned to make space for individual fibers of thepulp but being substantially smaller than the size of said flocks, andmoving said walls relative to each other in a direction perpendicular tothe main flow direction of the pulp through said walls whereby to tearapart and disperse the fibers of flocks flowing through said walls.

2. A method as claimed in claim 1, wherein said walls are disposed closeto the outlet of the head box.

3. A method for dispersing flocks of agglomerated fibers in pulpconveyed to a paper machine so as to pass through a head box providedwith an outlet discharging the pulp from the head box to the wire ofsaid paper machine, comprising the steps of causing the pulp in saidhead box to flow towards said outlet substantially radially through twoconcentric perforated drum walls of circular cross section whilecrossing a small interspace between said walls, said interspace beingdimensioned to make space for individual fibers of the pulp but beingsubstantially smaller than the size of said flocks, and rotating saiddrum walls relative to each other, whereby to tear apart and disriersethe fibers of flocks flowing through said drum wal s.

4. A method as claimed in claim 3, wherein said drum walls are disposedclose to the outlet of the head box.

References Cited by the Examiner UNITED STATES PATENTS 409,201 8/89Hatch 162341 1,483,742 2/24 Nicol 241-90 1,841,693 1/32 Aldrich et a1.162342 2,736,246 2/56 Crittenden et a1. 162340 2,741,954 4/56 Allibe24190 2,929,449 3/60 Mardon et al. 162-341 DONALL H. SYLVESTER, PrimaryExaminer. MORRIS O. WOLK, Examiner.

1. A METHOD FOR DISPERSING FLOCKS OF AGGLOMERATED FIBERS IN PULPCONVEYED TO A PAPER MACHINE SO AS TO PASS THOUGH A HEAD BOX PROVIDEDWITH AN OUTLET DISCHARGING THE PULP FROM THE HEAD BOX TO THE WIRE OFSAID PAPER MACHINE, COMPRISING THE STEPS OF CAUSING THE PULP IN SAIDHEAD BOX TO FLOW TOWARD SAID OUTLET THROUGH TWO PERFORATED WALLS INSUCCESSION WHILE CROSSING A SMALL INTERSPACE BETWEEN SAID WALLS, SAIDINTERSPACE BEING DIMENSIONED TO